PMI Feedback Granularity for Subcarrier-Level Precoding

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Solution Overview

Problem

Existing wireless communication systems using subband-level precoding operations limit system performance due to low granularity, which affects multi-antenna technology like MIMO, leading to inefficiencies in multi-user interference elimination and signal processing.

Innovation Solution

Implementing subcarrier-level precoding technology by enhancing precoding granularity through methods such as determining PMI feedback and using precoding feedback frequency-domain granularity indication parameters to support subcarrier-level operations, reducing feedback overhead and improving communication system performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If subband-level precoding operations are used, then feedback overhead is reduced, but operation granularity is low which limits system performance

Engineering Contradiction:

Improvefeedback overheadVSAvoidoperation granularity

Core Design Contradiction:

Loss of informationVSManufacturing precision

Solution Approach 1:

The patent segments the frequency domain into subbands and applies different precoding granularity configurations to different subbands. Some subbands use subcarrier-level precoding (fine granularity) while others use subband-level precoding (coarse granularity), allowing the system to optimize between feedback overhead and performance on a per-subband basis.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic switching between subcarrier-level and subband-level precoding modes based on channel conditions, traffic type, and QoS requirements. The granularity configuration can be changed adaptively to match varying system demands, transitioning from static to dynamic operation.

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If subcarrier-level precoding is implemented, then operation granularity is improved, but feedback overhead increases

Engineering Contradiction:

Improveoperation granularityVSAvoidfeedback overhead

Core Design Contradiction:

Manufacturing precisionVSLoss of information

Solution Approach 1:

The patent applies different precoding granularity levels to different local regions (subbands) of the frequency domain based on local channel characteristics. Subbands with high frequency selectivity receive subcarrier-level precoding while others use subband-level precoding, optimizing the balance between granularity and overhead locally rather than uniformly across the entire bandwidth.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the granularity parameter dynamically based on channel conditions, traffic type, and QoS requirements. The system can switch between subcarrier-level and subband-level precoding by adjusting the granularity parameter, allowing flexible adaptation to different operating scenarios without being locked into a fixed configuration.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If subband-level precoding is used, then system complexity is reduced, but multi-user interference elimination is insufficient

Engineering Contradiction:

Improvesystem complexityVSAvoidmulti-user interference

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the frequency domain and applies different precoding strategies to different segments. By dividing the bandwidth into subbands and selectively applying subcarrier-level precoding to specific subbands, the system achieves better interference elimination without requiring subcarrier-level processing across the entire bandwidth, thus controlling complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses codebook-based precoding where pre-computed precoding matrices are stored and selected based on channel conditions. This copying approach avoids real-time complex calculations while still achieving effective interference elimination through the selection of appropriate precoding matrices from the codebook.

Inventive Principle:

Principle #26Copying

4Ease of operation

If subband-level precoding operations are applied, then signal processing difficulty is reduced, but system capacity is limited

Engineering Contradiction:

Improvesignal processing difficultyVSAvoidsystem capacity

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the precoding granularity parameter dynamically based on channel conditions and system demands. By adjusting this parameter, the system can transition between easier-to-process subband-level precoding and higher-capacity subcarrier-level precoding, optimizing the trade-off between processing ease and system capacity.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12537582B2Method for information transmission, method for determining precoding granularity, terminal and base station

Publication Date: 2026.01.27 NTT DOCOMO INC

AI summary

The present disclosure provides a method for precoding matrix indicator (PMI) transmission and a method for determining precoding granularity performed by a terminal, and a corresponding terminal and base station. The terminal includes: a receiving unit configured to receive first information about the precoding matrix indicator (PMI) from a base station of the communication system; and a control unit configured to determine whether to transmit second information about the precoding matrix indicator according to the first information, wherein the precoding matrix indicator is for a subcarrier-level precoding matrix.